1. Field of the Invention
The invention relates to an antenna switching circuit. Particularly, the invention relates to an antenna switching circuit connected to an external docking device and an electronic device and an antenna switching method thereof.
2. Description of Related Art
Vehicular telematics systems or industrial computers generally use a docking device to enhance convenience and performance of a computing device. Referring to FIG. 1, FIG. 1 is a schematic diagram of an electronic device connected to a docking device. The electronic device 10 includes a radio frequency (RF) module 11, an internal antenna 12 and a docking connector 13. The docking connector 13 is a mechanical docking connector which includes a first RF terminal 13A, a second RF terminal 13B and a third RF terminal 13C.
When the electronic device 10 is not connected to a docking device (not shown in FIG. 1), the first RF terminal 13A is electrically connected to the radio frequency module 11, and the second RF terminal 13B is electrically connected to the internal antenna 12. Therefore, the RF module 11 can transmit or receive RF signals through the internal antenna 12 of the electronic device 10.
When the electronic device 10 is connected to the docking device, the third RF terminal 13C is electrically connected to an external antenna 22 of the docking device. Thus, the electrical connection between the RF module 11 and the internal antenna 12 is disconnected, and the RF module 11 is electrically connected to the external antenna 22.
FIG. 2 is a schematic diagram illustrating a situation that a docking connector is not connected to a docking device. Referring to FIG. 2, the docking connector 13 is a mechanical docking connector. When the electronic device 10 is not connected to the docking device, a pogo connector 221 of the docking device is not in contact with the third RF terminal 13C. The first RF terminal 13A and the second RF terminal 13B are substantially in contact with each other, and the RF module 11 is electrically connected to the internal antenna 12.
FIG. 3 is a schematic diagram illustrating a situation that a docking connector is connected to a docking device. When the electronic device 10 is connected to the docking device, not only the pogo connector 221 of the docking device is substantially in contact with the third RF terminal 13C, but also the first RF terminal 13A and the second RF terminal 13B are separated from each other. In this way, the electrical connection between the RF module 11 and the internal antenna 12 is disconnected. The RF module 11 is electrically connected to the external antenna 22 through the docking connector 13 and the pogo connector 221.
The mechanical docking connector (the docking connector 13) has advantages of being simple in structure and easy in usage. However, reliability of the mechanical docking connector is gradually decreased after multiple plug/unplug operations. Moreover, the mechanical docking connector results in high loss of transmission power of the RF signal. Therefore, it is an important issue in the field to design a docking connector with low loss in transmission power and stable reliability.